Hi Doug. It's just a normal 12V 40A relay 25mm cube with spade terminals. I soldered a reverse biased diode across the coil terminals to stop back emf and connected to the D8 heated bed connection on RAMPS. You need to disable PID for the heat bed and just use bang bang. It works great

QuoteAndyCart
Hi Doug. It's just a normal 12V 40A relay 25mm cube with spade terminals. I soldered a reverse biased diode across the coil terminals to stop back emf and connected to the D8 heated bed connection on RAMPS. You need to disable PID for the heat bed and just use bang bang. It works great

Thanks Andy so just a automotive relay then. I Have an SSR that I got for it and it appears to be faulty ie it aint switching.

I am using a duet which I am in the middle of calibrating but the hot bed issue is a prob at the mo so will pop down to an auto place near me and pick one up and then Maplin's for a diode and reverse biased I guess is Cathode to the Neg return lead (Long time since I did any of this lol).

I do the same thing for the 12V heated bed, I had a few issues with the ramps board overheating when I direct powered the bed and tried to get the temps up for ABS printing. You definitely need to disable PID though, or the relay sounds more like a buzzer

Quotedougal1957Thanks Andy so just a automotive relay then. I Have an SSR that I got for it and it appears to be faulty ie it aint switching.

Make sure that you are using bang-bang and not PID, even with an SSR. They do not like switching at frequencies higher than 20 hertz from what I've read, and the result is that the SSR doesn't switch. (Does RepRapFirmware support bang-bang?) I know that Smoothieware has a setting for maximum hertz to use in PID with an SSR, which is how mine (24V DC) is set up and working.

Another thought is to verify that your SSR is an AC/DC and not DC/DC part number. Apparently the type of power being switched is important when buying an SSR.....

Quotedougal1957Thanks Andy so just a automotive relay then. I Have an SSR that I got for it and it appears to be faulty ie it aint switching.

Make sure that you are using bang-bang and not PID, even with an SSR. They do not like switching at frequencies higher than 20 hertz from what I've read, and the result is that the SSR doesn't switch. (Does RepRapFirmware support bang-bang?) I know that Smoothieware has a setting for maximum hertz to use in PID with an SSR, which is how mine (24V DC) is set up and working.

Another thought is to verify that your SSR is an AC/DC and not DC/DC part number. Apparently the type of power being switched is important when buying an SSR.....

Yes definitely the correct type even tested the Duet with a DCDC one I have and that lights up when on but the AC one I have doesn't so pretty much proves it I think and DC42's Firmware by default is BangBang for the Hotbed.

Got it pretty well dialled in for the Endstop offsets just need to do the Delta Arm/Radius now but just been called out to a P1 Fault so back later.

Quotedougal1957
Yes definitely the correct type even tested the Duet with a DCDC one I have and that lights up when on but the AC one I have doesn't so pretty much proves it I think and DC42's Firmware by default is BangBang for the Hotbed.

Yes, unless you change it in config.g.

I presume you connected the input terminals of the SSR the right way round?

I purchased an SSR-10DA to control the mains-voltage heated bed of my enlarged mini-Kossel. These are widely available in the UK. They have an LED that lights up when they are energised, and a protective plastic cover to help keep things from touching the terminals. Personally, I wouldn't use a mechanical relay for this, since SSRs are ideal for controlling heaters and don't create so much interference as they turn on and off.

I've got it as far as I can go for now. I just need some Kapton Tape, so I can attach the thermistor to the heated bed, but that will have to wait until I get paid on the 25th. Before then it's the wife's birthday.

I added power and nothing blew up or started smoking. Then I used the auto-home option on the control panel and the carriages were moved up until they hit the limit switches. So, a good start.

Quotedougal1957
Yes definitely the correct type even tested the Duet with a DCDC one I have and that lights up when on but the AC one I have doesn't so pretty much proves it I think and DC42's Firmware by default is BangBang for the Hotbed.

Yes, unless you change it in config.g.

I presume you connected the input terminals of the SSR the right way round?.

Yes Did have it right way round first thing I thought of tried reversing the input connections and led didn't light either way tested with a DC DC one that I have and that did light up in sympathy with the Heatbed O/P Led on the Duet.

Quotedc42
I purchased an SSR-10DA to control the mains-voltage heated bed of my enlarged mini-Kossel. These are widely available in the UK. They have an LED that lights up when they are energised, and a protective plastic cover to help keep things from touching the terminals. Personally, I wouldn't use a mechanical relay for this, since SSRs are ideal for controlling heaters and don't create so much interference as they turn on and off.

I have another pair of SSR-25DA's coming to replace it one for the delta and one for the CoreXY.

I've never had much luck with solid state relays. I wasn't aware of the 20Hz limit though. Mine were rated at 50A. I had one AC one and one DC one. I would be surprised if either could sink more than 10A without overheating though.

@ Doug. The diode on your automotive relay needs the cathode (grey stripe on the body) to go to the 12V side. I use a 1N4001 rectifier diode. Back EMF is always in the opposite polarity to the voltage across the coil hence putting the diode 'back to front' in normal use its as if it's not there but as soon as the coil voltage is removed and the opposite polarity back EMF is induced it just shorts out across the diode. It can reach 10000V or so so you don't want it anywhere near your electronics !

Quotedougal1957Yes Did have it right way round first thing I thought of tried reversing the input connections and led didn't light either way tested with a DC DC one that I have and that did light up in sympathy with the Heatbed O/P Led on the Duet.

Unless the SSR has input reverse polarity protection, applying more than about 5V to the input terminals may might damage it, because both the visible and IR LEDs are likely to break down. I suggest connecting the SSR input to the EXT_FET terminals on the Duet instead of the heated bed output terminals, to avoid this risk.

QuoteAndyCart
I've never had much luck with solid state relays. I wasn't aware of the 20Hz limit though. Mine were rated at 50A. I had one AC one and one DC one. I would be surprised if either could sink more than 10A without overheating though.

A zero-crossing DC-AC SSR won't work properly with even 20Hz PWM, because it only passes complete half-cycles of mains. So 1Hz PWM is more like it.

SSRs in general can only be run at or near their rated current with a generous heatsink. I chose the SSR-10DA (rated at 10A RMS) on the basis that I won't be putting more than 2A through it.

Quotedougal1957Yes Did have it right way round first thing I thought of tried reversing the input connections and led didn't light either way tested with a DC DC one that I have and that did light up in sympathy with the Heatbed O/P Led on the Duet.

Unless the SSR has input reverse polarity protection, applying more than about 5V to the input terminals may might damage it, because both the visible and IR LEDs are likely to break down. I suggest connecting the SSR input to the EXT_FET terminals on the Duet instead of the heated bed output terminals, to avoid this risk.

Thanks for that tip dave will re-wire it in the morning I have managed to get an American 25A one locally for a fiver so will try that.

It's just occurred to me that the EXT_FET pins may not have enough juice to turn on the SSR, because there is a 1K resistor to +5V in that circuit. So using the heated bed output may be the best bet - but be sure to get the polarity right.

QuoteDavid J
I'm making really good progress with printing the plastic parts and collecting the bits & pieces, and hope to start assembly very soon. However, I still have three quick questions:

What size and type of screws should I use to fasten the rod carrier to the mini_v_wheel carriage? M3 screws into the undersized holes, or self-tapping screws?

What sort of screws should I use to fasten the covers to the top brackets?

How far should the extrusions extend above the top brackets?

All answers gratefully accepted!

Cheers,
David

Rod carrier fixing screws are 10mm No.4 self tappers, top bracket fixing screws are M3 x 25mm tapped into the plastic pillars on the covers, extrusion through top bracket, about 8mm. Actually just enough to engage the square section in the cover.

Not quite right. There's a good picture by gowen a couple of pages back

45mm bolt with an M5 washer through the hole in the top bracket
M5 washer
Bearing
Bearing
M5 washer
M5 nut

The 45mm bolt serves double duty. It holds the top bracket to the extrusion via the T nut and also holds the top idler assembly. Set the height of the bracket by measuring from the base (allowing about 8mm of extrusion to protrude, but it's the base to top measure that's critical in that all three towers need to be the same) then tighten the bolt against the extrusion T nut to secure. Then nip up the M5 nut that holds the idler bearings tight together.

I worked out that I needed a baud rate of 115200 in Repetier-Host and I set a nominal circular build area of 200mm dia by 250mm high. Then to check my connection I used the manual controls to move the effector. When I tried to shift it horizontally, the Z carriage shot downwards, the Z effector strut went past horizontal and before I could pull the plug the struts started pinging off, much to the amusement of my colleagues.

Could someone tell me the Cherry Pi settings I need for Repetier host and possibly a short guide on running auto-calibration?

It's closer to the rostock-style of hotend mount, but it still has the auto-probing mechanism that Andy developed. You have to flip your carriages over for my holes to line up though.
I'm using a metal E3D hotend on it, with their stock fan.

QuoteZzyzxx71
I took Andy's updated 8mm all metal hot end effector and Maso's 10mm ball bearing effector and merged them

Looks good, man! I had designed mine before seeing the all-metal effector, and this looks like a great dovetail between the two.

It looks like you still have the two holes for hinge springs on there, which you won't need anymore. But doesn't Andy's spring string mount now use two holes? So you could put three holes on the underside to screw down the strings if you wanted.

Also, you don't have a bottom face on that. Must've gotten deleted somewhere.

Can someone help me out with a printing problem? I'm trying to print the E3D Mount Base v2.stl file on my Prusa i3, but I'm getting strange results. The 2 ribs that fit into the 6mm groove at the top of the E3Dv6 keep coming out with a spacing of 6.2mm, which of course won't work. Assuming that this isn't a designed dimension then the only conclusion is that I have a printing problem - although other items are coming out at the correct size.

- I have re-checked the filament calibration - it was actually under-supplying, pushing through 95mm instead of the 100mm requested. This has now been set to exactly the right value.
- I'm printing according to Andy's guidelines - 0.3 layer height, 3 solid layers top and bottom, 2 perimiters.
- I've used both Cura and Slic3r, using what I think are sensible parameters. I get the same results from both.
- Looking at the file in Netfab, I can see that the total height of my printed part is near-enough correct.

Netfab also suggests that this dimension *is* about 6.2mm in the STL file, so I'm well confused...

David

(I've attached the technical drawing for the E3Dv6 as a discussion point)